Maybe it's a reaction to the "universal translator" thing so common in SF.
Or maybe I just like playing with grammar and syntax.
NaNo 2003: the main character encounters people who don't speak her language and have imperfect translator machines. Much grammatical mangling ensues.
NaNo 2004: one of the important secondary characters and the POV character have no common language. Fortunately another main character is fluent in both languages, even if it isn't always around.
A short story I'm working on right now: the main character is travelling with (and learning about) a creature who only knows a little bit of her language. Much grammatical mangling ensues.
An older short story I found again recently: the main character meets other characters and they have no common language or written symbols in common. I may work on this one again, and add more grammatical mangling.
A pair of other short stories I wrote several years ago: one of the important characters in each story has no means of verbal communication with the other characters and must communicate by other means.
See a trend here?